Senator presses NRC on issues at Calif nuke plant

FILE - In this June 30, 2011 file photo, beach-goers walk on the sand near the San Onofre nuclear power plant in San Clemente, Calif. A report commissioned by an environmental group warned Tuesday, May 15, 2012 that running California's San Onofre nuclear plant at reduced power would not resolve problems with badly worn tubing that have kept its twin reactors offline for more than three months, and might make it worse. (AP Photo, Lenny Ignelzi, File)
— AP

FILE - In this June 30, 2011 file photo, beach-goers walk on the sand near the San Onofre nuclear power plant in San Clemente, Calif. A report commissioned by an environmental group warned Tuesday, May 15, 2012 that running California's San Onofre nuclear plant at reduced power would not resolve problems with badly worn tubing that have kept its twin reactors offline for more than three months, and might make it worse. (AP Photo, Lenny Ignelzi, File)
/ AP

LOS ANGELES 
The chair of the U.S. Senate's environment committee pressed federal regulators Tuesday to disclose details about the design of the troubled steam generators at the San Onofre nuclear power plant, where a probe into tube damage has kept the reactors sidelined for months.

In a letter, Sen. Barbara Boxer asked Nuclear Regulatory Commission Chairman Gregory Jaczko for documentation on how the federal agency reviewed generator modifications, which might be the culprit in vibration that has damaged hundreds of tubes inside the complex machines.

At issue is whether operator Southern California Edison sidestepped any federal requirements by conducting extensive design changes, a claim leveled by an environmental group that said the alterations are at the heart of the plant's problems.

The twin reactors, located along the coast between San Diego and Los Angeles, have been shut down for more than three months while investigators try to determine the cause of the unusual tube wear.

"Concerns have been raised that design changes in the steam generators contributed to accelerated wear in tubes carrying radioactive water," Boxer, D-Calif., wrote in a similar letter to SCE parent Edison International that also requested documents from the company on the history of the equipment. "The determination to restart the San Onofre reactors must ensure the safety of the millions of Californians who live and work near the plant."

Boxer chairs the Environment and Public Works Committee.

Edison said in a statement Monday that "the NRC was fully informed that the replacement would be conducted under the same regulations as had been previously applied at other plants."

The 13-page report issued by Friends of the Earth warned that running the nuclear plant at reduced power would not resolve problems with badly worn tubing. Earlier this month the company announced a tentative plan to restart and run the seaside reactors at lower power, at least for several months, because engineers believe that will ease vibration that might be the culprit in heavy tube wear.

The generators function something like a car radiator, which controls heat in a vehicle's engine. The generator tubes circulate hot, radioactive water from the reactors, which heat a bath of non-radioactive water surrounding them. That makes steam, which is used to turn turbines to make electricity.

The tubes represent a critical safety barrier - if a tube breaks, there is the potential that radioactivity can escape into the atmosphere. Also, serious leaks can drain protective cooling water from a reactor.

The four generators each have nearly 10,000 alloy tubes that carry radioactive water.

The report by Friends of the Earth also expanded an earlier allegation that Southern California Edison misled federal regulators about the modifications, a claim disputed by the Nuclear Regulatory Commission and the company.

The trouble began to unfold in January, when the Unit 3 reactor was shut down as a precaution after a tube break. Traces of radiation escaped at the time, but officials said there was no danger to workers or neighbors. Unit 2 had been taken offline earlier that month for maintenance, but investigators later found unexpected wear on hundreds of tubes in both units.